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Merge pull request #28301 from berrange/cvm-lockdown

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Avoid using SMBIOS for kernel cmdline injection in sd-stub in confidential VMs
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Luca Boccassi 2023-07-14 22:47:37 +01:00 committed by GitHub
parent 8ced74d76b 4b1153cfcc
commit d3634ac46b
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GPG key ID: 4AEE18F83AFDEB23
5 changed files with 206 additions and 76 deletions
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67
src/basic/confidential-virt.c
View file

@ -5,81 +5,16 @@
#endif
#include <errno.h>
#include <fcntl.h>
#include <stdint.h>
#include <stdlib.h>
#include <unistd.h>
#include "confidential-virt-fundamental.h"
#include "confidential-virt.h"
#include "fd-util.h"
#include "missing_threads.h"
#include "string-table.h"
#include "utf8.h"
#define CPUID_PROCESSOR_INFO_AND_FEATURE_BITS UINT32_C(0x1)
/*
* AMD64 Architecture Programmer’s Manual Volume 3:
* General-Purpose and System Instructions.
* Chapter: E4.1 - Maximum Extended Function Number and Vendor String
* https://www.amd.com/system/files/TechDocs/24594.pdf
*/
#define CPUID_GET_HIGHEST_FUNCTION UINT32_C(0x80000000)
/*
* AMD64 Architecture Programmer’s Manual Volume 3:
* General-Purpose and System Instructions.
* Chapter: E4.17 - Encrypted Memory Capabilities
* https://www.amd.com/system/files/TechDocs/24594.pdf
*/
#define CPUID_AMD_GET_ENCRYPTED_MEMORY_CAPABILITIES UINT32_C(0x8000001f)
/*
* AMD64 Architecture Programmer’s Manual Volume 3:
* General-Purpose and System Instructions.
* Chapter: 15.34.10 - SEV_STATUS MSR
* https://www.amd.com/system/files/TechDocs/24593.pdf
*/
#define MSR_AMD64_SEV UINT32_C(0xc0010131)
/*
* Intel® TDX Module v1.5 Base Architecture Specification
* Chapter: 11.2
* https://www.intel.com/content/www/us/en/content-details/733575/intel-tdx-module-v1-5-base-architecture-specification.html
*/
#define CPUID_INTEL_TDX_ENUMERATION UINT32_C(0x21)
/* Requirements for Implementing the Microsoft Hypervisor Interface
* https://learn.microsoft.com/en-us/virtualization/hyper-v-on-windows/tlfs/tlfs
*/
#define CPUID_HYPERV_VENDOR_AND_MAX_FUNCTIONS UINT32_C(0x40000000)
#define CPUID_HYPERV_FEATURES UINT32_C(0x40000003)
#define CPUID_HYPERV_ISOLATION_CONFIG UINT32_C(0x4000000C)
#define CPUID_HYPERV_MIN UINT32_C(0x40000005)
#define CPUID_HYPERV_MAX UINT32_C(0x4000ffff)
#define CPUID_SIG_AMD "AuthenticAMD"
#define CPUID_SIG_INTEL "GenuineIntel"
#define CPUID_SIG_INTEL_TDX "IntelTDX "
#define CPUID_SIG_HYPERV "Microsoft Hv"
/* ecx bit 31: set => hyperpvisor, unset => bare metal */
#define CPUID_FEATURE_HYPERVISOR (UINT32_C(1) << 31)
/* Linux include/asm-generic/hyperv-tlfs.h */
#define CPUID_HYPERV_CPU_MANAGEMENT (UINT32_C(1) << 12) /* root partition */
#define CPUID_HYPERV_ISOLATION (UINT32_C(1) << 22) /* confidential VM partition */
#define CPUID_HYPERV_ISOLATION_TYPE_MASK UINT32_C(0xf)
#define CPUID_HYPERV_ISOLATION_TYPE_SNP 2
#define EAX_SEV (UINT32_C(1) << 1)
#define MSR_SEV (UINT64_C(1) << 0)
#define MSR_SEV_ES (UINT64_C(1) << 1)
#define MSR_SEV_SNP (UINT64_C(1) << 2)
#if defined(__x86_64__)

24
src/boot/efi/stub.c
View file

@ -489,17 +489,21 @@ static EFI_STATUS run(EFI_HANDLE image) {
log_error_status(err, "Error loading UKI-specific addons, ignoring: %m");
parameters_measured = parameters_measured < 0 ? m : (parameters_measured && m);
const char *extra = smbios_find_oem_string("io.systemd.stub.kernel-cmdline-extra");
if (extra) {
_cleanup_free_ char16_t *tmp = TAKE_PTR(cmdline), *extra16 = xstr8_to_16(extra);
cmdline = xasprintf("%ls %ls", tmp, extra16);
/* SMBIOS OEM Strings data is controlled by the host admin and not covered
* by the VM attestation, so MUST NOT be trusted when in a confidential VM */
if (!is_confidential_vm()) {
const char *extra = smbios_find_oem_string("io.systemd.stub.kernel-cmdline-extra");
if (extra) {
_cleanup_free_ char16_t *tmp = TAKE_PTR(cmdline), *extra16 = xstr8_to_16(extra);
cmdline = xasprintf("%ls %ls", tmp, extra16);
/* SMBIOS strings are measured in PCR1, but we also want to measure them in our specific
* PCR12, as firmware-owned PCRs are very difficult to use as they'll contain unpredictable
* measurements that are not under control of the machine owner. */
m = false;
(void) tpm_log_load_options(extra16, &m);
parameters_measured = parameters_measured < 0 ? m : (parameters_measured && m);
/* SMBIOS strings are measured in PCR1, but we also want to measure them in our specific
* PCR12, as firmware-owned PCRs are very difficult to use as they'll contain unpredictable
* measurements that are not under control of the machine owner. */
m = false;
(void) tpm_log_load_options(extra16, &m);
parameters_measured = parameters_measured < 0 ? m : (parameters_measured && m);
}
}
export_variables(loaded_image);

117
src/boot/efi/vmm.c
View file

@ -4,6 +4,7 @@
# include <cpuid.h>
#endif
#include "confidential-virt-fundamental.h"
#include "device-path-util.h"
#include "drivers.h"
#include "efi-string.h"
@ -307,3 +308,119 @@ const char* smbios_find_oem_string(const char *name) {
return NULL;
}
#if defined(__i386__) || defined(__x86_64__)
static uint32_t cpuid_leaf(uint32_t eax, char ret_sig[static 13], bool swapped) {
/* zero-init as some queries explicitly require subleaf == 0 */
uint32_t sig[3] = {};
if (swapped)
__cpuid_count(eax, 0, eax, sig[0], sig[2], sig[1]);
else
__cpuid_count(eax, 0, eax, sig[0], sig[1], sig[2]);
memcpy(ret_sig, sig, sizeof(sig));
ret_sig[12] = 0; /* \0-terminate the string to make string comparison possible */
return eax;
}
static uint64_t msr(uint32_t index) {
uint64_t val;
#ifdef __x86_64__
uint32_t low, high;
asm volatile ("rdmsr" : "=a"(low), "=d"(high) : "c"(index) : "memory");
val = ((uint64_t)high << 32) | low;
#else
asm volatile ("rdmsr" : "=A"(val) : "c"(index) : "memory");
#endif
return val;
}
static bool detect_hyperv_sev(void) {
uint32_t eax, ebx, ecx, edx, feat;
char sig[13] = {};
feat = cpuid_leaf(CPUID_HYPERV_VENDOR_AND_MAX_FUNCTIONS, sig, false);
if (feat < CPUID_HYPERV_MIN || feat > CPUID_HYPERV_MAX)
return false;
if (memcmp(sig, CPUID_SIG_HYPERV, sizeof(sig)) != 0)
return false;
__cpuid(CPUID_HYPERV_FEATURES, eax, ebx, ecx, edx);
if (ebx & CPUID_HYPERV_ISOLATION && !(ebx & CPUID_HYPERV_CPU_MANAGEMENT)) {
__cpuid(CPUID_HYPERV_ISOLATION_CONFIG, eax, ebx, ecx, edx);
if ((ebx & CPUID_HYPERV_ISOLATION_TYPE_MASK) == CPUID_HYPERV_ISOLATION_TYPE_SNP)
return true;
}
return false;
}
static bool detect_sev(void) {
uint32_t eax, ebx, ecx, edx;
uint64_t msrval;
__cpuid(CPUID_GET_HIGHEST_FUNCTION, eax, ebx, ecx, edx);
if (eax < CPUID_AMD_GET_ENCRYPTED_MEMORY_CAPABILITIES)
return false;
__cpuid(CPUID_AMD_GET_ENCRYPTED_MEMORY_CAPABILITIES, eax, ebx, ecx, edx);
/* bit 1 == CPU supports SEV feature
*
* Note, Azure blocks this CPUID leaf from its SEV-SNP
* guests, so we must fallback to trying some HyperV
* specific CPUID checks.
*/
if (!(eax & EAX_SEV))
return detect_hyperv_sev();
msrval = msr(MSR_AMD64_SEV);
if (msrval & (MSR_SEV_SNP | MSR_SEV_ES | MSR_SEV))
return true;
return false;
}
static bool detect_tdx(void) {
uint32_t eax, ebx, ecx, edx;
char sig[13] = {};
__cpuid(CPUID_GET_HIGHEST_FUNCTION, eax, ebx, ecx, edx);
if (eax < CPUID_INTEL_TDX_ENUMERATION)
return false;
cpuid_leaf(CPUID_INTEL_TDX_ENUMERATION, sig, true);
if (memcmp(sig, CPUID_SIG_INTEL_TDX, sizeof(sig)) == 0)
return true;
return false;
}
#endif /* ! __i386__ && ! __x86_64__ */
bool is_confidential_vm(void) {
#if defined(__i386__) || defined(__x86_64__)
char sig[13] = {};
if (!cpuid_in_hypervisor())
return false;
cpuid_leaf(0, sig, true);
if (memcmp(sig, CPUID_SIG_AMD, sizeof(sig)) == 0)
return detect_sev();
if (memcmp(sig, CPUID_SIG_INTEL, sizeof(sig)) == 0)
return detect_tdx();
#endif /* ! __i386__ && ! __x86_64__ */
return false;
}

2
src/boot/efi/vmm.h
View file

@ -8,4 +8,6 @@ EFI_STATUS vmm_open(EFI_HANDLE *ret_qemu_dev, EFI_FILE **ret_qemu_dir);
bool in_hypervisor(void);
bool is_confidential_vm(void);
const char* smbios_find_oem_string(const char *name);

72
src/fundamental/confidential-virt-fundamental.h Normal file
View file

@ -0,0 +1,72 @@
/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <stdint.h>
/* Keep CVM detection logic in this file at feature parity with
* that in src/efi/boot/vmm.c */
#define CPUID_PROCESSOR_INFO_AND_FEATURE_BITS UINT32_C(0x1)
/*
* AMD64 Architecture Programmer’s Manual Volume 3:
* General-Purpose and System Instructions.
* Chapter: E4.1 - Maximum Extended Function Number and Vendor String
* https://www.amd.com/system/files/TechDocs/24594.pdf
*/
#define CPUID_GET_HIGHEST_FUNCTION UINT32_C(0x80000000)
/*
* AMD64 Architecture Programmer’s Manual Volume 3:
* General-Purpose and System Instructions.
* Chapter: E4.17 - Encrypted Memory Capabilities
* https://www.amd.com/system/files/TechDocs/24594.pdf
*/
#define CPUID_AMD_GET_ENCRYPTED_MEMORY_CAPABILITIES UINT32_C(0x8000001f)
/*
* AMD64 Architecture Programmer’s Manual Volume 3:
* General-Purpose and System Instructions.
* Chapter: 15.34.10 - SEV_STATUS MSR
* https://www.amd.com/system/files/TechDocs/24593.pdf
*/
#define MSR_AMD64_SEV UINT32_C(0xc0010131)
/*
* Intel® TDX Module v1.5 Base Architecture Specification
* Chapter: 11.2
* https://www.intel.com/content/www/us/en/content-details/733575/intel-tdx-module-v1-5-base-architecture-specification.html
*/
#define CPUID_INTEL_TDX_ENUMERATION UINT32_C(0x21)
/* Requirements for Implementing the Microsoft Hypervisor Interface
* https://learn.microsoft.com/en-us/virtualization/hyper-v-on-windows/tlfs/tlfs
*/
#define CPUID_HYPERV_VENDOR_AND_MAX_FUNCTIONS UINT32_C(0x40000000)
#define CPUID_HYPERV_FEATURES UINT32_C(0x40000003)
#define CPUID_HYPERV_ISOLATION_CONFIG UINT32_C(0x4000000C)
#define CPUID_HYPERV_MIN UINT32_C(0x40000005)
#define CPUID_HYPERV_MAX UINT32_C(0x4000ffff)
#define CPUID_SIG_AMD "AuthenticAMD"
#define CPUID_SIG_INTEL "GenuineIntel"
#define CPUID_SIG_INTEL_TDX "IntelTDX "
#define CPUID_SIG_HYPERV "Microsoft Hv"
/* ecx bit 31: set => hyperpvisor, unset => bare metal */
#define CPUID_FEATURE_HYPERVISOR (UINT32_C(1) << 31)
/* Linux include/asm-generic/hyperv-tlfs.h */
#define CPUID_HYPERV_CPU_MANAGEMENT (UINT32_C(1) << 12) /* root partition */
#define CPUID_HYPERV_ISOLATION (UINT32_C(1) << 22) /* confidential VM partition */
#define CPUID_HYPERV_ISOLATION_TYPE_MASK UINT32_C(0xf)
#define CPUID_HYPERV_ISOLATION_TYPE_SNP 2
#define EAX_SEV (UINT32_C(1) << 1)
#define MSR_SEV (UINT64_C(1) << 0)
#define MSR_SEV_ES (UINT64_C(1) << 1)
#define MSR_SEV_SNP (UINT64_C(1) << 2)